Here’s how Rule 19.2(c) works: At Position 2 in the diagram, Bert was clear astern of Ann and required by Rule 12 to keep clear of her. Ann was sailing as close to the shore as it was safe to sail. If Bert had established an overlap between Ann and the shore and, at the moment the overlap began, there was not room for Bert to pass between Ann and the shore, Rule 19.2(c) states that Bert would not be entitled to room under Rule 19.2(b). Therefore Ann would not be required to move over and give Bert safe passage inside. Provided that Ann was indeed sailing as close to the shore as was safe, the odds are that Bert would run aground. And, if he did, Ann would not have broken any rule.
Let’s now look at how Rules 19.2(b) and (c) work at Positions 3, 4, 5 and 6.